91 Ford Probe A/C and heater fan won't work

I have a got a 91 ford probe four cylinder automatic with 80,000 miles on it the a/c and heater fan won't do anything I have no power at the fan and the will work if I unplug everything and run a hot and ground to it. I took the speed switch out of the dash and only one wire is hot coming in I don't know if this is the way it should be or not the wire that is hot is a black and yellow striped wire it is the same wire that supplies the power to the a/c light (the only thing that works) some body please help me!